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Biomedical subjects

M C Johnson

Publications and source records attributed to M C Johnson.

18 recordsLinked to original sources
PubMed1979

Powder mixing in direct compression formulation by ordered and random processes.

The mixing processes taking place in a two component system involving a cohesive drug, tetracycline and a direct compression vehicle, spray dried lactose (SDL), have been studied by chemical analysis of powder samples and fluorescence microscopy. At a drug concentration level of 0.25% w/w, both random and ordered mixing is taking place. Mixture quality is better (Cv = 1%) using a fine grade of crystalline lactose (CL) than with SDL (Cv = 4%). Using fractionated material, it was found that SDL between 106 and 300 micron gave Cv values up to 12%, whereas with SDL below 106 micron values of 2% were obtained. The poor quality of the SDL mixtures is attributed to ordered unit segregation.

Chemistry, Pharmaceutical↗
PubMed1979

Diagnosis of tuberculosis: routine cultures of bronchial washings are not indicated.

During a five-year period, cultures of bronchial washings for Mycobacterium tuberculosis were obtained almost routinely (859 of 1,012 bronchoscopic examinations.). This practice proved costly, and the diagnostic yield was extremely low. Only three cases were diagnosed solely by this method (0.35 percent). Five other cases were false-positive. Additionally, 39 patients with known active pulmonary tuberculosis had false-negative cultures of bronchial washings; 13 of these 39 patients were receiving antituberculosis drugs at the time of their bronchoscopic examinations. The inhibitory effect of local anesthetics upon the growth of M tuberculosis is the possible cause for the remaining 26 false-negative cultures. We conclude that bronchoscopic examination and culture of bronchial washings are not the best sources for diagnosis of pulmonary tuberculosis and that cultures of sputum and/or gastric washings are usually sufficient. The practice of obtaining routine cultures of bronchial washings in known pulmonary tuberculosis is of questionable value, when nearly two-thirds may be false-negative.

Aged↗
PubMed1979

Effect of inhibitors of arachidonic acid metabolism on mitogenesis in human lymphocytes: possible role of thromboxanes and products of the lipoxygenase pathway.

Although it is already known that prostaglandins inhibit lymphocyte responses to mitogens the role of other products of arachidonic acid (AA) metabolism has not previously been investigated. Various inhibitors of AA metabolism were studied for their effects on mitogenesis in human lymphocytes, including imidazole, benzylimidazole, N-0164, L-8027, 5, 8, 11, 14 eicosatetraynoic acid, nordihydroguaiaretic acid, indomethacin, and aspirin. Selective or partially selective inhibitors of thromboxane synthesis, such as imidazole, benzylimidazole, N-0164, and L-8027 inhibited the mitogenic response at concentrations that also substantially affect thromboxane B2 synthesis in platelet-free lymphocyte preparations. Since indomethacin failed to reverse the inhibition by imidazole or N-0164, it is probably due to decreased thromboxane synthesis per se rather than secondary increases in prostaglandin synthesis. Eicosatetraynoic acid and nordihydroguaiaretic acid were more effective inhibitors of mitogenesis than of thromboxane synthesis. Since these agents also affect the lipoxygenase pathway, it is possible that part of their action is at this level. Thus, in addition to the inhibitory effects of prostaglandins on mitogenesis, other products of AA metabolism may promote the response.

Antilymphocyte Serum↗
PubMed1978

Radioisotope scanning in the initial staging of bronchogenic carcinoma.

The use of routine radioisotope scanning to screen for subclinical metastatic disease in the initial staging of bronchogenic carcinoma was studied. To define the value of scans, liver, brain, and bone scans were studied prospectively in 111 patients and retrospectively in 114 patients. Among patients with clinical findings suggesting metastatic disease, 14.4 per cent of the liver scans, 12.3 per cent of the brain scans, and 35.7 per cent of the bone scans were positive. All patients free of clinical findings had negative liver and brain scans. Positive bone scans occurred in 8 per cent of the patients without clinical abnormalities. True-positive bone scans occurred in less than 4 per cent of the patients free of clinical abnormalities. The clinical findings noted in the patients pointed to the organ involved in only 76 per cent of the abnormal liver scans, 62 per cent of the abnormal brain scans, and 75 per cent of the abnormal bone scans. Clinical findings associated with positive liver and brain scans were multiple and significant, whereas findings with the positive bone scans could be few or subtle. Routine scanning failed to identify a significant number of patients with clinically unsuspected metastatic disease. Liver, brain, and bone scanning is indicated only in patients suspected of having metastatic disease.

Adult↗
PubMed1978

Quantitative thyroid fluorescent scanning: technique and clinical experience.

A method for quantifying thyroid gland iodine content using a modified fluorescence scanning system is described. The technique does not require a computer. Two single channel analyzers and digital scalers are used to determine net counts from iodine k-alpha x-rays and system response in counts per milligram is calibrated from studies of known quantities of iodine placed in thyroid phantoms. Fluorescence quantification of thyroid gland iodine content was performed in 250 patients with a wide variety of thyroid disorders. Thirty euthyroid patients judged to have no evidence of thyroid disease averaged 10.1 +/- 3.9 mg glandular iodine. Results for several major diagnostic categories were: untreated Graves' disease, 28 patients, 24.4 +/- 9.9 mg; diffuse euthyroid goiter, 14 patients, 16.1 +/- 7.4 mg; primary hypothyroidism, seven patients, 0.5 mg; and nontoxic multinodular goiter, 28 patients, 7.3 +/- 4.1 mg. Follow-up studies on patients treated for Graves' disease both medically and with 131I generally revealed elevated iodine contents in persistently hyperthyroid patients, lower than normal average amounts in euthyroid patients, and only trace amounts in hypothyroid patients. Although the clinical role of fluorescence iodine quantification remains to be fully established, the technique provides information not otherwise available on an important parameter of thyroid status.

Fluorescence↗
PubMed1977

Ultrastructural localization of sucrases in Streptococcus mutans GS-5 and an extracellular polysaccharide mutant: a comparative cytochemical and immunocytochemical study.

Electron microscopy and cytochemical and immunocytochemical procedures were used to study the ultrastructural distribution of sucrase enzymes in two strains of Streptococcus mutans. In a strongly adherent and virulent parent strain, GS-5, most of the invertase and fructosyltransferase activities were demonstrated extracellularly or bound to the cell surfaces. Intracellularly, enzymatic sites were detected near the plasma membrane on the periphery of the nucleoid and central mesosome. In GS-511, a mutant of diminished virulence and adherence, most of the enzymatic activity was not located on the cell surfaces, but was found away from the cell walls and associated with extracellular polysaccharides. Intracellularly, GS-511 manifested the same distribution of invertase and fructosyltransferase as did GS-5; however, the close association of these enzymes with the plasma membrane was not shown in GS-511. In both strains, extracellular areas near regions associated with cross wall formation appeared to show localized concentrations of these sucrases. Antibodies against partially purified glucosyltransferase (GTF) enzymes from GS-5 were used to localize GTF by immunocytochemical techniques. Indirect ferritin localization procedures showed that the extracellular and cell-bound GTF enzymes were distributed in similar locations as the fructosyltransferase and invertase enzymes. By absorption of the antiserum with whole GS-511 cells, the location of extracellular GTF and surface antigens unique to GS-5 was demonstrated. The dramatically reduced levels of cell-bound sucrase activity in GS-511 indicates the significant role of these enzymes in adherence and cariogenicity.

Cell Membrane↗
PubMed1977

Biochemical study of the relationship of extracellular glucan to adherence and cariogenicity in Streptococcus mutans and an extracellular polysaccharide mutant.

A mutant of Streptococcus mutans, GS-5, which differed in extracellular polysaccharide (EPS) produced from sucrose, was used to study the role of EPS in the production of dental caries. The mutant proved to be identical to the parent strain in sugar fermentation, growth rate, and serotype. Strain GS-5 synthesized an EPS, which in electron micrographs appeared to be of fibrillar structure, whereas the mutant produced no fibrillar material but only a globular EPS. Analysis of the EPS revealed that about 30% of the glucose units in the GS-5 polymer carried (1-3)-like bonds either as branch points or as part of the linear backbone and that the mutant material contained only about 3% of these linkages. When grown in sucrose broth, the proportion of the mutant culture adherent to the glass vessel was dramatically less than that of the parent strain. Caries scores produced in conventional rats by the mutant were significantly lower than those obtained with the parent strain. Since the only difference discovered between strain GS-5 and the mutant was the inability of the mutant to synthesize either a fibrillar EPS or an EPS with more than about 3% (1-3)-like linkages, it was concluded that the fibrillar EPS of strain GS-5 contained about 30% (1-3)-like linkages and was necessary for adherence of the bacteria to surfaces and for production of dental caries in test animals.

Animals↗
PubMed1977

Evaluation of a thyroid fluorescent scanning system of concentric source-detector design.

A concentric source-detector system for thyroid fluorescent scanning is described, including fundamental parameters of system response and adaptation of a conventional rectilinear scanner for use with it. The basic system consists of twenty 1-Ci sources of 241Am, a 500-mm2 Si(Li) detector, and associated pulse-height electronics. The image-forming equipment of the rectilinear scanner is retained. We have developed a clinical imaging technique that provides a photon density of 600-800 counts/cm2 over the thyroid gland in subjects with normal iodine pools. Comparisons are made between the outrigger design for fluorescent scanning and conventional emission scanning.

Americium↗
PubMed1977

Solitary autonomous thyroid nodules: comparison of fluorescent and pertechnetate imaging.

Twelve patients with solitary autonomous thyroid nodules were scanned with [99mTc] pertechnetate and by fluorescent imaging. Nodular dimensions were essentially identical on the two types of scans, but the relative scan densities in the nodular versus extranodular areas demonstrated striking differences. In 11 of the 12 patients, the ratio of nodular-to-extranodular radiotracer accumulation was significantly higher than the ratio of nodular-to-extranodular iodine content. In two patients with no demonstrable extranodular radiotracer accumulation by initial pertechnetate scan, extra-nodular tissue was demonstrated by fluorescent imaging. In such cases, fluorescent scanning may eliminate the need for a second radionuclide scan following TSH stimulation to visualize the extranodular tissue. Fluorescent scanning offers a unique new method for aiding the evaluation of patients with suspected autonomous nodules, and can facilitate the diagnosis in some cases. The maintenance of relatively uniform iodine concentration between nodular and extranodular tissues is an intriguing finding that bears further investigation.

Adolescent↗
PubMed1976

Solitary abnormalities in bone scans of patients with extraosseous malignancies.

The incidence and significance of solitary bone scan abnormalities were assessed in a study of 1,129 consecutive patients with extraskeletal primary malignancies. Solitary abnormalities were encountered in 172 cases (15%). The etiology of the scan abnormality was established in 90 of the 172 cases; 58 (64%) were due to metastatic disease, and 32 (36%) were secondary to a benign process. A significant percentage of solitary scan abnormalities is due to benign disease processes, even in patients with proved extraosseous malignancies.

Bone Neoplasms↗
PubMed1976

Body-background defects with 99mTc-DTPA after renal transplantation: case reports.

Photon-deficient areas adjacent to transplanted kidneys were seen in the early phases of several dynamic studies obtained with 99mTc-diethylenetri-aminepentaacetic acid (99mTc-DTPA). The causes included hematoma, urinoma, and lymphocele. These fluid collections do not readily exchange as part of the extracellular space and, if sufficiently large, may be visualized as photon-deficient areas in the normally homogeneous background of 99mTc-DTPA studies.

Adult↗
PubMed1975

Abnormal radionuclide deposition patterns adjacent to focal skeletal lesions.

A scintigraphic pattern is described for bone scans with 99m-Tc-polyphosphate and 99m-Tc-diphosphonate in which abnormal tracer accumulation extends beyond the known limits of certain skeletal lesions. The associated pathologic entities include benign and malignant tumors, infection, and trauma. The pathogenesis of "extended patterns" has not been proved but probably relates to regional hyperemia induced by associated lesions. Increased blood flow results in more tracer delivery to otherwise normal bone in the "watershed" areas of hyperemia, producing these patterns.

Bone Diseases↗